BACKGROUND
1. Field
[0001] The present disclosure is directed to a method and apparatus for reducing latency
of Long Term Evolution uplink transmissions. More particularly, the present disclosure
is directed to resource selection for reducing latency of Long Term Evolution uplink
transmissions.
2. Introduction
[0002] Presently, wireless communication devices, such as smartphones, cellular phones,
tablets, personal computers, and other devices, communicate using wireless signals
over networks, such as over a Long Term Evolution (LTE) cellular network. Many of
the communications are sensitive to latency, such as communication delays, that slows
down the transfer of data. Unfortunately, there is latency in current systems due
to negotiations that a communication device must perform with a base station to transmit
data. For example, to transmit data, a device must first request a grant from a base
station to transmit the data and then wait for the grant before transmitting the data.
This results in undesirable latency that delays communication between the communication
device and the network.
[0003] Thus, there is a need for a method and apparatus for reducing latency of LTE uplink
transmissions.
[0005] US 2011/0243080 describes methods of contention-based transmission. A base station first transmits
contention-based configuration information and also grant to a user equipment (UE).
The UE transmits uplink contention-based data via one of the transmission opportunities.
[0006] US 2013/0102320 describes contention based uplink transmission. When uplink grant includes CB-RNTI,
a scheduling unit randomly selects one radio resource from multiple radio resources
indicated by this uplink grant. The scheduling unit generates control information
for controlling the transmission unit so that PUSCH is multiplexed on the selected
radio resource, and outputs it to the control unit.
[0007] US 2012/0300711 describes signaling configuration of a Physical Uplink Shared Channel (PUSCH). A
base station sends Downlink Control Information (DCI) to the target user equipment
through a Physical Downlink Control Channel (PUCCH); and the downlink control information
includes orthogonal cover code information and/or cyclic shift information for scheduling
the physical uplink shared channel in the multi-antenna port transmission and/or single
antenna port transmission.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] In order to describe the manner in which advantages and features of the disclosure
can be obtained, a description of the disclosure is rendered by reference to specific
embodiments thereof which are illustrated in the appended drawings. These drawings
depict only example embodiments of the disclosure and are not therefore to be considered
to be limiting of its scope.
FIG. 1 is an example block diagram of a system according to a possible embodiment;
FIG. 2 is an example signal flow diagram illustrating signals between a wireless communication
device and a base station required to transmit an uplink packet using a current LTE
uplink mechanism;
FIG. 3 is an example signal flow diagram illustrating signals associated with an uplink
packet transmission between a wireless communication device and a base station using
contention-based uplink mechanism according to a possible embodiment;
FIG. 4 is an example flowchart illustrating operation of a user equipment for a basic
contention-based resource selection scheme according to a possible embodiment;
FIG. 5 is an example flowchart illustrating operation of a wireless communication
device according to a possible embodiment;
FIG. 6 is an example flowchart illustrating operation of a wireless communication
device according to a possible embodiment;
FIG. 7 is an example flowchart illustrating operation of a wireless communication
device according to a possible embodiment; and
FIG. 8 is an example block diagram of an apparatus according to a possible embodiment.
DETAILED DESCRIPTION
[0009] According to the present invention, a method as set forth in claim 1 and an apparatus
as set forth in claim 12, for reducing latency of LTE uplink transmission, are provided.
Embodiments of the invention are claimed in the dependent claims.
[0010] According to a possible embodiment, configuration information regarding a Downlink
Control Information (DCI) message for a Physical Uplink Shared Channel (PUSCH) transmission
can be acquired. The DCI message can be received on a Physical Downlink Control Channel
(PDCCH) in a first subframe. A PDCCH can be a PDCCH that is demodulated based on cell-specific
reference signals or an enhanced PDCCH (EPDCCH) that is demodulated based on dedicated
reference signals, or a further enhanced physical downlink control channel or a combination
thereof. The DCI message can indicate a plurality of resource assignments in a second
subframe for an uplink carrier from which a User Equipment (UE) can select one resource
assignment for transmission on the uplink carrier. The DCI message can be Cyclic Redundancy
Check (CRC) scrambled by a Radio Network Temporary Identifier (RNTI) that is indicated
via higher layers that are higher than a physical layer. A resource assignment can
be selected from the plurality of resource assignments using a selection criterion.
A data packet can be transmitted on the PUSCH in a resource of the selected resource
assignment in the second subframe on the uplink carrier.
[0011] According to a possible embodiment, a DCI message can be received in a first subframe.
The DCI message can indicate a resource assignment and a modulation and coding scheme
and can indicate a plurality of cyclic shifts from which a UE may select one cyclic
shift for transmission in a second subframe for an uplink carrier. A cyclic shift
can be selected from the plurality of indicated cyclic shifts based on a selection
criterion. A data packet can be transmitted on a PUSCH in a resource indicated by
the resource assignment and modulation and coding scheme and using a Demodulation
Reference Signal (DMRS) based on the selected cyclic shift in the second subframe
on the uplink carrier.
[0012] According to a possible embodiment, an indication can be acquired, where the indication
can indicate a set of frequency domain resource blocks for possible PUSCH transmission
in an uplink subframe. A subset of resource blocks can be selected from the set of
frequency domain resource blocks for possible PUSCH transmission based on a selection
criterion. The selection criterion can use at least a resource set size acquired from
the indication, can use a modulo function, and can use an identifier associated with
the UE, where a modulo function can be expressed as "mod(
a,
b)" or as "
amod
b," which can denote the remainder after dividing
a by
b. The PUSCH can be transmitted in the selected subset of resource blocks in the uplink
subframe. The time duration (or transmit time interval or subframe duration) for the
reduced latency PUSCH may be defined to be similar to Rel-8 TTI size of 1 millisecond,
or may be shorter, such as half millisecond, and this can be configurable by the network
based on the desired latency reduction target or application. In another example,
the frequency domain resource block for possible PUSCH transmission for reduced latency
may be defined to be identical to Rel-8 LTE, or it may be defined to correspond to
a short transmit time interval, such as 0.5ms instead of 1ms. In a further example,
the set of resource blocks available for possible PUSCH transmission may be configured
only in a subset of subframes of possible uplink subframes. For example, the set of
resource blocks may be available in every alternate subframe, RB0-RB6 can be available
for possible PUSCH transmission in subframes indexed 0,2,4..., etc, and each RB can
be 1 millisecond in duration.
[0013] FIG. 1 is an example block diagram of a system 100 according to a possible embodiment.
The system 100 can include a wireless communication device 110, such as UE, a base
station 120, such as an enhanced NodeB (eNB), and a network 130. The wireless communication
device 110 can be a wireless terminal, a portable wireless communication device, a
smartphone, a cellular telephone, a flip phone, a personal digital assistant, a device
having a subscriber identity module, a personal computer, a selective call receiver,
a tablet computer, a laptop computer, or any other device that is capable of sending
and receiving communication signals on a wireless network.
[0014] The network 130 can include any type of network that is capable of sending and receiving
wireless communication signals. For example, the network 130 can include a wireless
communication network, a cellular telephone network, a Time Division Multiple Access
(TDMA)-based network, a Code Division Multiple Access (CDMA)-based network, an Orthogonal
Frequency Division Multiple Access (OFDMA)-based network, a Long Term Evolution (LTE)
network, a 3rd Generation Partnership Project (3GPP)-based network, a satellite communications
network, a high altitude platform network, and/or other communications networks.
[0015] The uplink communications from the UE to the eNB utilize Single Carrier FDM(A) (SC-FDMA)
or DFT-Spread OFDM(A) (DFT-SOFDM(A)) according to the LTE standard. In SC-FDM or DFT-SOFDM,
block transmission of QAM data symbols can be performed by first discrete Fourier
transform (DFT)-spreading (or precoding) followed by subcarrier mapping and OFDM modulation
with a conventional OFDM modulator. The use of DFT precoding can allow a moderate
cubic metric /peak-to-average power ratio (PAPR) which can lead to reduced cost, size
and power consumption of the UE power amplifier. In accordance with DFT-SOFDM, each
subcarrier used for uplink transmission can include information for all the transmitted
modulated signals, with the input data stream being spread over them. Uplink data
can be transmitted using PUSCH. While embodiments describe uplink packet transmission
based on the LTE standard, it is noted that the same techniques can applied for uplink
transmissions based on other modulation schemes such as conventional OFDM and other
transmission schemes.
[0016] Embodiments can provide for resource allocation and resource selection aspects of
reduced latency LTE uplink transmissions. Latency reduction for a user's data packets
can provide better user experience, reduced complexity, such as reduced buffering
requirements and other reduced complexity, and improved performance, such as faster
link adaptation/feedback, improved TCP performance, and other improved performance
while also supporting new applications that may be delay critical, such as augmented
reality applications, vehicular communication applications, and other applications
that may be delay critical.
[0017] For a UE in Radio Resource Control_Connected (RRC_CONNECTED) state, the UE can typically
look for downlink grants in every downlink subframe, which can be one millisecond
duration. If an eNB receives a packet that is to be transmitted to a UE, it can immediately
transmit that packet to the UE in the next downlink subframe using the control and
data channels in the subframe, such as PDCCH or an EPDCCH and a Physical Downlink
Shared Channel (PDSCH).
[0018] FIG. 2 is an example signal flow diagram illustrating the signals between the wireless
communication device 110, such as a UE, and the base station 120, such as an eNB,
required to transmit an uplink packet using a current LTE uplink mechanism. For uplink
packet transmission, if an uplink buffer of the device 110 is empty and the device
110 receives an uplink packet in its buffer at 210, typically first the device 110
has to send a Scheduling Request (SR) to the base station 120 at 220, then the base
station 120 sends an uplink grant to the device 110 at 230, and then the device 110
transmits the packet on the resources indicated by the base station 120 at 240. Each
of the three steps adds to the overall delay that transmission of an uplink packet
can experience. Typically, the SR resource is a dedicated resource for a UE, which
is configured with a certain periodicity, such as every 5ms/2ms/10ms, etc. Latency
for SR transmission can be reduced by providing the UE an SR opportunity on a much
more frequent basis, such as by configuring a 2ms periodicity for all UEs, but this
can lead to significantly increased overhead on the uplink.
[0019] FIG. 3 is an example signal flow diagram illustrating signals associated with an
uplink packet transmission between the wireless communication device 110, such as
a UE, and the base station 120, such as an eNB, using a Contention-Based Uplink (CB-UL)
mechanism according to a possible embodiment. At 310, the base station 120 can send
a contention-based uplink grant, such as via a broadcast or other message, to the
device 110. At 320, the device 110 can have an uplink packet ready to transmit. At
330 the device 110 can transmit the uplink packet to the base station 120 using information
from the uplink grant. For example, embodiments can avoid the latency due to SR for
some uplink transmissions. This can be done by scheduling CB-UL. In this case, an
eNB can transmit an uplink grant in its cell, and any UE can utilize that grant to
prepare and transmit its uplink packet. The UE can embed certain information in the
packet, such as a Medium Access Control Identifier (MAC ID), a Cell Radio Network
Temporary Identifier (C-RNTI), and other information so the eNB can determine which
UE sent the packet. In another example, a group of UEs configured for CB-UL and possibly
addressed, such as by group Contention-Based RNTI CB-RNTI, by the UL grant can use
a particular resource assignment in the UL grant.
[0020] The contention-based uplink grant can be sent using DCI format 0/1A and/or 1C that
support more compact payload sizes relative to some other DCI formats. The grant can
be sent in any search space, such as Common Search Space (CSS) or UE-specific Search
Space (UESS). In some cases, a CB-UL-Downlink Control Information (CB-UL-DCI) format
is aligned with the size of an existing DCI format that the UE searches. Additional
blind decodes can also be supported by the UE if the CB-UL-DCI format size is not
aligned with an existing DCI format size. For example, four additional blind decodes
can be supported in the common search space to support CB-UL-DCI. A special RNTI,
such as a CB-RNTI, that is configured via higher layers may be used to distinguish
the CB-UL-DCI format from other formats. Alternately, explicit fields may be included
in DCI 0/1A and/or 1C to distinguish the CB-UL grant from other grants carried in
the DCI format.
[0021] For Enhanced Physical Downlink Control Channel (EPDCCH) UESS, the UESS may be overlapping
for a group of UEs. Therefore, the CB-uplink grant can be sent in the UE-specific
search space. Then the CB-uplink DCI format payload size may be aligned to the UE's
DCI format 0/1A/ payload size in the UESS.
[0022] According to a possible embodiment, a UE may transmit a packet with low-latency.
To transmit the packet, the UE can indicate to the network that it is interested and/or
capable of supporting latency reduction on the uplink and the UE can acquire configuration
information regarding a DCI message for a Physical Uplink Shared Channel (PUSCH) transmission.
The base station may indicate that it can support latency reduction on the uplink
via a system information broadcast message or using reserved fields in master information
block or dedicated message. A UE may, upon receiving the indication, in turn indicate
to the network that it is capable of supporting low-latency also. Then the base station
can send configuration information to the UE via system information broadcast message
or dedicated message. Alternatively, the network may grant, implicitly or explicitly,
a set of UEs camped on the cell to operate in the CB mode under the condition that
they have the capability of supporting latency reduction. The network may be aware
of such a capability via UE category/capability information. The UE can be in a Radio
Resource Control Connected (RRC_Connected) state, and can be performing Radio Resource
Management (RRM) measurements, such as measurements including pathloss estimate and
other measurements, and can be maintaining uplink time alignment, such as when a Timing
Alignment timer is not expired, based on network commands, such as Timing Advance
(TA) commands, and based on the UE's own timing adjustments based on downlink received
timing. The UE can then acquire information, such as via Medium Access Control (MAC),
RRC, or other sources of information, indicating a set or multiple set of resources
for possible contention based (CB) PUSCH transmission. The UE may also acquire other
information such as set of open loop power control parameters (P0, alpha, etc.), set
of modulation and coding scheme parameters, redundancy version, virtual cell identity
used for e.g., reference signal generation, and other information, that is also relevant
for transmission of the CB PUSCH transmission. When the UE has data in its UL buffer
and the data is to be transmitted with low latency, it can search a downlink control
region to detect an uplink grant intended for the UE, such as from a first DCI message
via DCI format 0/4 with CRC scrambled with UE's C-RNTI. The contention-based PUSCH
transmissions may be configured only on primary cell or on a subset of cells configured
for the UE.
[0023] If UE does not detect DCI intended for the UE, the UE can detect second DCI message
with a second RNTI. For example, the UE can receive the second DCI message on a Physical
Downlink Control Channel (PDCCH) in a first subframe. The second DCI message can indicate
a plurality of resource assignments in a second subframe for a first carrier from
which the UE selects one resource assignment for transmission on the first carrier.
The second DCI message can be Cyclic Redundancy Check (CRC) scrambled by a Radio Network
Temporary Identifier (RNTI) that is indicated via higher layers that are higher than
a physical layer. For example, the second DCI message can indicate a plurality of
resource assignments that are a subset of resource assignments indicated by the information
acquired via MAC, RRC, and/or another DCI message. The UE can then use a selection
method to select a subset of UL resources from the set of resources for possible CB
transmission in UL subframe n+k, where k may be fixed, such as to 4 in Frequency Division
Duplex (FDD), and k may be variable e.g. based on Time Division Duplex (TDD) Uplink/Downlink
(UL/DL) configuration in TDD. The selection method can include the UE choosing one
or more of the following: a number of Resource Blocks (RBs), an MCS index, transport
block size, Demodulation Reference Signal (DMRS) cyclic shift, and DMRS Orthogonal
cover code (OCC) sequence. The UE can then transmit PUSCH using the selected UL resources
and associated parameters, such as modulation & coding scheme, power control settings,
and other parameters, to transmit the UL data. The UE may also embed its identifier,
such as a UE Identifier (UE ID) or C-RNTI, or other UE identifier, that an eNB can
utilize to detect which UE sent the associated PUSCH transmission. The UE may also
include a buffer status report in the associated PUSCH. If eNB successfully detects
the PUSCH, then the eNB can acknowledge the packet reception by sending feedback to
the UE using the Physical Hybrid-Automatic Repeat Request (ARQ) Indicator Channel
(PHICH) or by sending an explicit downlink message addressed to the UE. The UE can
then clear the contents of the UL buffer. The PUSCH that is transmitted based on contention-based
resource can also be denoted as low-latency PUSCH.
[0024] Embodiments can provide for multiple resource assignments in a single grant. For
example, the common-search space, such as on PDCCH, may be overloaded and can provide
only a limited number of transmission opportunities where only 4 grants can be transmitted
and a Common Search Space (CSS) capacity is 16 CCEs. Therefore, for CB-uplink, a single
CB-based grant can schedule uplink on multiple uplink resources in a given subframe.
When extra blind decodes are allowed to accommodate the CB uplink transmissions, then
an extended common-search space may be defined using the System Information Radio
Network Temporary Identifier (SI-RNTI) or CB-RNTI with more candidates for aggregation
levels 4 or 8, and/or additional candidates for aggregation levels 1 and 2. New common
search space with different aggregation levels (e.g. 2,4,8,16) may be defined for
EPDCCH.
[0025] A first example of CB-grant fields indicating a plurality of resource assignments
can include a 0/1A differentiation field. The CB-grant fields can include fields for
first resource assignment including a frequency hopping flag, a RB assignment field,
MCS, TPC for PUSCH, and cyclic shift for DMRS and OCC index. The CB-grant fields can
include fields for a second resource assignment including a frequency hopping flag,
a RB assignment, MCS, TPC for PUSCH, and cyclic shift for DMRS and OCC index. The
CB-grant fields can also include a resource Allocation (RA) type. These fields can
be part of a DCI message. To maintain consistent DCI message size, fields of current
DCI messages that are not useful for a CB-grant can be replaced with the additional
CB-grant fields. Table 1 illustrates example fields and description of DCI format
1A. Example fields that can be replaced with CB-grant fields include an NDI field,
a TPC for PUSCH field, a cyclic shift for DMRS and OCC index field, a CSI request
field, and other fields. Table 1 also illustrates example fields and description of
DCI format 1C, where the number of bits in 1C can be 12 bits (5 MHz), 13 (10 MHz),
15 (20 MHz), or any other useful number of bits.
Table 1. Fields and description of DCI format 0 and 1C
Field in DCI format 1A |
Number of bits |
Additional information |
carrier indicator field |
0 or 3 |
May be used typically on UESS only |
0/1A differentiation field |
1 |
|
Freq hopping flag |
1 |
|
RB assignment |
variable |
|
MCS |
5 |
|
NDI |
1 |
|
TPC for PUSCH |
2 |
|
Cyclic shift for DMRS and OCC index |
3 |
|
UL index |
2 |
May be used only for TDD |
DAI |
2 |
May be used only for TDD Primary cell |
CSI request |
1 or 2 |
2-bits can be used for CA and DCI mapped to UESS |
SRS request |
1 or 2 |
May be used only for DCI mapped to UESS |
RA type |
1 |
May be present only when UL Sys BW<DL sys BW |
Field in DCI 1C |
Number of bits |
Additional information |
Gap value |
1 |
|
RB assignment |
Variable |
depends on the DL system bandwidth and Gap |
MCS |
5 |
|
[0026] In a second example, one or more grants may be jointly coded to reduce payload or
to fit the grant into existing UL DCI payloads. In this example, the CB-grant fields
can include a 0/1A differentiation field. The CB-grant fields can also include fields
for first and second resource assignment including a field to interpret joint assignment,
a joint frequency hopping flag, a joint RB assignment field, joint MCS, Joint Transmit
Power Control (TPC) for PUSCH, and joint Cyclic shift for DMRS and OCC index selection.
The CB-grant fields can also include the RA type.
[0027] To elaborate on an example, there can be a field to interpret joint assignment, which
when set to 0 can indicate there is no second resource assignment. If that field is
set to 1, it can imply that there is a second resource assignment in the grant. If
the RB assignment field indicates that RBO and RB1 are part of the first resource
assignment, then the second resource assignment can be the next two resource blocks,
RB2 and RB3. The joint MCS field can indicate a single MCS is used for both resource
assignments. A UE that receives such an uplink grant can select one of the resource
assignments based on a random selection or using a set of predetermined rules. For
instance, if the number of RBs for each resource assignment is not the same, then
the UE can select the resource assignment based on its uplink buffer status. The UE
can also select a resource assignment based on a pathloss value threshold. The threshold
may be configured via higher layer signaling.
[0028] Embodiments can provide for UE autonomous selection from a contention-based resource
region. For example, to reduce latency for uplink packets, an eNB may configure, such
as via higher layers, a set of resource blocks in the uplink or a frequency region
in the uplink system bandwidth. These resources can be used by any UE or a set of
UEs to transmit on the uplink, which can include a Buffer Status Report (BSR). The
resources can be advertised in a SIB, in a RRC message, and/or in any other useful
message, and can be used by the UE any time it wants to transmit a packet with low
latency, without having to wait for SR transmission, or in other useful instances.
For example, the UE can acquire an indication from the eNB that indicates a set of
frequency domain resource blocks for possible PUSCH transmission in an uplink subframe.
[0029] The configured resources can be implicitly indicated. For instance, resources used
for Device to Device (D2D) or sidelink operation can also be used to indicate resources
to be used for advertised uplink resources. For TDD Enhanced Interference Mitigation
and Traffic Adaptation (EIMTA), the set of uplink resources used for CB-uplink may
be limited to the uplink subframes indicated by the TDD configuration corresponding
to the DL-reference UL/DL configuration. In another option, the set of UL resources
to be used for CB-uplink may be determined using the UL/DL configuration indicated
by the dynamic UL/DL configuration indicated in the DCI format 1C with CRC scrambled
by EIMTA-RNTI. In another example, the resources can be indicated by RACH resources/configuration.
Since RACH resources are allocated by a cell to serve UEs camped on that cell, the
number of UEs attached to that cell can implicitly be taken into account. Therefore,
that information can be used to allocate the number of CB-UL resources. For instance,
the CB-UL resources can be determined based on a formula which takes into account
the RACH configuration.
[0030] As another example, a subset of RACH resources can be reused for CB-UL resources.
In one simple example, all PRACH resources can be reused as CB-UL resources. For instance,
PRACH configuration index 45 can have 6 RB resources available every odd subframe
that can be reused for CB UL transmissions. In this particular example, no extra signaling
may be needed to inform UEs about CB-UL resources. This approach may require extra
detection processes at the eNB side.
[0031] The eNB can configure, such as via higher layers, a set of Modulation and Coding
Scheme (MCS) and/or transport block sizes that the UE may use to transmit an uplink
packet in the configured resources. Alternatively, such configuration may be fixed
in specifications, for example, if contention-based uplink is used to transmit BSR
or other fixed size payload. MCS and/or TBS can also be dependent on other parameters,
for instance, the channel quality of the link between UE and the eNB, such as in a
case of TDD operation, where reciprocity may be assumed. The eNB can also configure,
such as via higher layers, a set of cyclic shifts and/or cover code sequences that
any UE can use to transmit DMRS along with an uplink packet in the configured resources.
[0032] The eNB can additionally configure, such as via higher layers, a set of PHICH resources,
such as for sending ACK/NACK feedback information associated with uplink transmissions
in the configured resources, that a UE can use to receive feedback about its uplink
transmission in a configured resource. The eNB can further configure, such as via
higher layers, a separate set of power control setting parameters, such as P0, alpha,
and other power control settings that a UE use for transmitting on the uplink in the
configured resources. The eNB can also control the use of the higher layer configured
uplink resources dynamically via physical and/or MAC layer signaling.
[0033] According to a first implementation, an eNB can configure a set of resource blocks
(e.g. RB0, RB1, RB2, RB4) for contention-based uplink and eNB can expect a UE to pick
one resource block and transmit on that resource block. The UE can select the resource
block based on a hashing function which can be based on UE's C-RNTI, Subframe number,
System Frame Number, a set configuration index, UE-eNB link quality, determined Cyclic
Shift (CS) and Orthogonal Cover Code (OCC) index, and other useful information. For
example, UE can pick one RB of the set of RB indexed by (L
∗ M + C-RNTI + SFN) mod N_RBs, where L is selected from the {0, 1, 2,... N_RBs-1},
N_RBs is the number of RB in the set of RBs, M is a constant, and M and N_RBs are
relatively prime to each other.
[0034] According to a second implementation, an eNB can configure a set of starting resource
blocks (e.g. RB0, RB1, RB2, RB4) for contention-based uplink and the UE can transmit
on
L contiguous resources starting at one of the allowed starting resource blocks from
the set. The allowed values of
L can be pre-configured or signaled via higher layers, and a UE can select a particular
value of
L based on the packet or Transport Block (TB) it is attempting to communicate to the
eNB. For instance, if the UE wants to communicate a 15 byte transport block, then
with 24-bit CRC, the number of information bits can be 15
∗8+24 = 144 bits, and for 1 RB (14 x 14 = 144 REs), QPSK modulation, can correspond
to a coding rate of ½. If the UE has a packet size of 33 bytes, then it can choose
to transmit the TB using a 2-RB allocation, for achieving the same coding rate of
½. The UE can use a first orthogonal cover code (OCC) for a 1-RB allocation, and a
second orthogonal cover code for a 2-RB allocation. The CS used by the UE for 1-RB
and 2-RB allocation can be the same or different.
[0035] According to a third implementation, an eNB can configure a set of resource blocks
(e.g. RB0, RB1, RB2, RB4) for contention-based uplink, a set of resource allocations
(e.g. 1,2,4 RB allocations), a set of MCSes (QPSK-rate-1/2, QPSK, rate-3/4, 16QAM-rate-1/2,
etc), a set of Transport Block Sizes (TBSes) (6 bytes of TCP-ACK with additional L2/L3
header, 320 bits of VoIP packet, etc), a set of cyclic shifts (a subset from the allowed
set), and/or other configurations. The UE can select from the set of allowed combinations
based on its requirement, such as an amount of uplink data to transmit, and can use
at least a hashing function that is dependent on at least one of the UE's C-RNTI,
Subframe number, System Frame Number, a set configuration index, and/or other information.
[0036] According to a fourth implementation, an eNB can configure multiple sets of contention-based
uplink resources, each set having one of starting resource blocks (e.g. RB0, RB1,
RB2, RB4), and a set of resource allocations (e.g. 1, 2, 4 RB allocations), a set
of MCSes (QPSK-rate-1/2, QPSK, rate-3/4, 16QAM-rate-1/2, etc), a set of TBSes (6 bytes
of TCP-ACK with additional L2/L3 header, 320 bits of VoIP packet, etc), a set of cyclic
shifts (a subset from the allowed set), and/or other configurations. The UE can select
one set from the multiple sets of based on its requirement, such as the amount of
uplink data to transmit, and from that set, can use a resource based on at least a
hashing function that is dependent on at least one of the UE's C-RNTI, Subframe number,
System Frame Number, a set configuration index, and/or other information. Each set
may be associated with a resource allocation. For example, a first set can have allocations
of 1 RB only, a second set may have allocation of 2 RB only, etc.
[0037] The above implementations illustrate ways of having an eNB configure resources at
higher layer and can rely on eNB blind decoding in the set of allowed resources to
detect uplink transmissions from UEs that are using these resources. The number of
blind decodes can be limited. For instance, the transmission length in RBs can be
indicated to the eNB by means of implicit/explicit indication. One example of explicit
indication could be the first "m" bits of each, or a subset of, RB(s) can be allocated
to represent RB index. The RB index can illustrate how many RBs are utilized for this
transmission. In another example, a subset of RBs can be used for a single RB transmission,
while another subset could be used for 2 RB transmissions and so on. For instance,
all CB-RBs can be used for single RB transmission, while 2 RB transmissions may only
be allowed in certain resources, and so on.
[0038] According to a fifth implementation, an eNB can configure multiple sets of contention-based
uplink resources, each set having one of starting resource blocks (e.g. RB0, RB1,
RB2, RB4), and a set of resource allocations (e.g. 1,2,4 RB allocations), a set of
MCSes (QPSK-rate-1/2, QPSK, rate-3/4, 16QAM-rate-1/2, etc), a set of TBSes (6 bytes
of TCP-ACK with additional L2/L3 header, 320 bits of VoIP packet, etc), a set of cyclic
shifts (a subset from the allowed set), and/or configurations. The UE can select one
set from the multiple sets based on its requirement, such as an amount of uplink data
to transmit, and/or at least based on a physical layer signaling. Thus, an eNB can
control the contention based resources based on physical layer signaling. The physical
layer signaling can be based on one or more fields within a common DCI transmitted
over a control channel. For instance, the DCI can have a one-bit indicator associated
with a set indicating whether a UE can use the set or not use the set in a corresponding
subframe. For instance, if the UE receives the DCI in downlink subframe n, the corresponding
fields may apply to uplink sets in subframe n+4 or in a pre-determined uplink subframe,
such as n+k, where k can be signaled by eNB or based on a UE capability indicated
to the network or based on a set of configurations such as TDD configuration. An example
is shown in Table 2. In another example, for instance, the DCI can have a one-bit
indicator associated with each set indicating whether a UE can use the set or not
use the set in a corresponding subframe.
Table 2: Uplink Type C Resource Indicator Field
Value of the Uplink Type C Resource Indicator Field |
Description |
'00' |
First set of uplink resources configured by higher layers |
'01' |
Second set of uplink resources configured by higher layers |
'10' |
Third set of uplink resources configured by higher layers |
'11' |
Fourth set of uplink resources configured by higher layers |
[0039] Based on the above, only 2-bits may be adequate in the DCI format, but similar fields
can be used for also controlling the MCS indicator, TBS indicator, and other information
as shown in Table 3.
Table 3: Uplink Type C Resource/MCS Indicator Field
Value of the Uplink Type C Resource/MCS Field |
Description |
'00' |
First set of uplink resources configured by higher layers, and a first set of MCS |
'01' |
Second set of uplink resources configured by higher layers and a second set of MCS |
'10' |
Third set of uplink resources configured by higher layers and a third set of MCS |
'11' |
Fourth set of uplink resources configured by higher layers and fourth set of MCS |
[0040] According to a sixth implementation, resources can be a fraction of a RB in time
domain. For instance, the UL portion of the TDD special subframe(s) can be configured
as a CB resource.
[0041] An eNB can configure a set of resource blocks for contention-based grant region.
The can UE perform a hashing function to determine a starting RB and a number of RBs
from the set. One of four RRC signaled sets may be as follows:
- 1. {RB3-6 (Slot 1), RB94-97(Slot 2)}
- 2. {RB13-16(Slot 1), RB84-87(Slot 2)}
- 3. {RB23-26(Slot 1), RB74-77(Slot 2)}
- 4. {RB33-36(Slot 1), RB64-67(Slot 2)}
[0042] The set may be defined such that UE does frequency hopping across slots for frequency
diversity. A grant can signal the sets allowed, and the UE can select a resource from
the allowed sets based on a hashing function. Persistent resources can be allocated,
such as one set per subframe, and the set in a given subframe can be a function of
the subframe index. Additionally, the eNB may signal multiple sets in a subframe using
dynamic signaling. A subset of TB sizes and/or resource allocation size allowed for
contention-based grants may be configured by the eNB. A subset of MCS allowed for
contention-based grants may be configured by the eNB. If the UE already sent multiple
packets in multiple subframes, such as in consecutive subframes, then it can allow
other UEs to use the resource. For example, it can perform some backoff or transmit
with a smaller probability than its previous attempt. The eNB can configure the probability
with which a UE transmits in multiple subframes. The UE may send a contention-based
uplink transmission in a subframe only if it has no uplink grant, such as a UE-specific
grant, for transmission in the subframe.
[0043] An eNB can configure a set of resource blocks for contention-based grant region using
a bitmap indication, such as via higher layers, where the bitmap indication can indicate
whether a particular resource block belongs to the contention-based grant region.
For instance, if the uplink system bandwidth corresponds to 100 resource blocks (indexed
RB0, RB1,... RB99), then the contention-based grant region can be indicated using
a 100-bit bitmap (b0, b1,.... b99), and if bit b0 is set to 1, then the corresponding
resource block RBO can belong to the contention-based grant region, otherwise RBO
may not belong to the contention-based grant region.
[0044] In another example, the higher layer can indicate parameters that can be used to
derive a corresponding bitmap, such as indicating a resource block offset, and a number
of resource blocks. For example, the eNB may indicate a first offset (O1), and a number
of resource blocks (N1), and a second offset (02), such that a resource block RBx
belongs to the contention-based region, if O1 <=x<O1+N1 or if O2-N1 < x <=O2. If the
uplink system bandwidth corresponds to 100 resource blocks (indexed RB0, RB1,... RB99),
then if higher layers indicate O1 = 10, O2 = 25, and N1 = 5, then a RBx (0<=x, 99)
belongs to the contention-based grant region if 10<=x<15 or if 20<x<=25, i.e. the
RBs belonging to the contention-based region can be given by {RB10, RB11, RB12, RB13,
RB14, RB20, RB21, RB22, RB23, RB24}.
[0045] FIG. 4 is an example flowchart 400 illustrating the operation of a UE for a basic
CB resource selection scheme according to a possible embodiment. At 410, the flowchart
can begin. At 420, the UE can determine whether it has UL data in its buffer. If the
UE has UL data in its buffer, at 430, the UE can determine whether it has received
an UL grant CRC scrambled with C-RNTI. If so, at 440 the UE can transmit in resources
indicated by the UL grant. If not, at 450 the UE can determine if there are possible
CB UL resources available in a subframe. If so, at 460 the UE can select a CB resource
and at 470 the UE can transmit in the selected resource. At 480, the flowchart can
end.
[0046] Embodiments can provide for resource selection, such as selection of a subset of
resource blocks, using a hashing function. For example, an uplink resource set, such
as a set of frequency domain resource blocks, can include of a set of uplink resources,
such as resource blocks, numbered from 0 to
NCCE,k-1, where
NCCE,k can be the total number of resources configured in that set in the subframe k. The
set of UL resource candidates that a UE may transmit on can be in terms of resource
spaces, where a resource space
at resource aggregation level
L, such as
L ∈ {1,2,4,8}, can be defined by a set of UL resource candidates. The UL resources
corresponding to UL resource candidate m of the resource space
can be given by:
where
Yk can be defined as described below and
i=0,···
,L-1. For the common resource space,
m'=
m. For the UE specific resource space,
m'=
m, where
m=0,···,
M(L)-1.
M(L) can be the number of UL resource candidates that a UE can be allowed to transmit
on in the given resource space. In a first example, the UE may be allowed to select
from a set of resource candidates, such as shown in Example 1 in Table 4, where each
resource candidate can correspond to a subset of resource blocks. In a second example,
the UE can obtain the resource candidate to transmit on directly, such as shown in
Example 2 in Table 4. The RA levels defining the resource space also are listed in
Table 4.
Table 4: Number of candidates for resource selection
Resource space
|
Example 1: Number of candidates M(L) |
Example 2: Number of candidates M(L) |
Type |
RA level L |
Size [in RBs] |
|
UE-specific |
1 RB |
6 |
1 |
2 RB |
6 |
1 |
4 RB |
2 |
1 |
8 RB |
2 |
1 |
Common |
4 RB |
2 |
1 |
8 RB |
2 |
1 |
[0047] For the common resource space,
Yk may be set to 0. In some cases, the common resource space may not be necessary or
the common resource space may be used for another purpose, such as when the UE has
a fixed payload to send.
[0048] For the UE-specific resource space
at RA level
L, the variable
Yk can be defined by
where example values can be
Y-1 =
nRNTI ≠ 0, A and D are relatively large prime number, such as
A = 39827,
D = 65537,
k = └
ns/2┘, and
ns can be the slot number within a radio frame. The slot number may be the slot number
of the UL subframe in which the UE transmits the uplink. For multi-RB allocations,
the RB allocations can be contiguous or non-contiguous based on the configuration
of the uplink resource set. The RNTI can be indicated via higher layers, and may be
either same or different from the UE's C-RNTI.
[0049] A second uplink resource set can also be configured with its own set of uplink resources.
The set of uplink resource candidates and the RA levels can be separately defined
or configured for each uplink resource set. The variable
Yk can also be defined separately for each uplink resource set, such as for A = 39829.
Other hashing functions, such as based on EPDCCH hashing, can also be used to determine
the UL resource candidate. It is noted that a UE can be configured with multiple uplink
resource sets, and it may apply the hashing function described herein separately in
each uplink resource set. In a given subframe, the UE can select a uplink resource
set based on random selection or based on the number of resource blocks that the UE
determines to transmit on.
Table 5: Number of candidates for resource selection.
Resource space
|
Example 1 - Number of candidates M(L) |
Example 2 - Number of candidates M(L) |
Type |
RA level L |
Size [in RBs] |
|
UE-specific |
1 RB |
2 |
1 |
2 RB |
2 |
1 |
4 RB |
- |
- |
8 RB |
- |
- |
Common |
4 RB |
1 |
1 |
8 RB |
- |
- |
[0050] Embodiments can provide for Scheduling Request (SR) operation under CB-UL transmission.
For example, if a UE has already transmitted in a CB-UL resource, but not received
an acknowledgment, the UE can transmit a scheduling request for a SR resource. If
the UE has received an acknowledgement for the UL transmission in the CB resource,
depending on factors such as data type, the UE may release the SR resource, and stop
(re-)transmitting a scheduling request. In one example, the UE can be configured with
SR and also can use CB-UL resources. The UE can be configured to select between using
SR and CB-UL based on its uplink buffer status. For example, if the uplink buffer
is smaller than a threshold, the UE can use CB-UL. Otherwise the UE can use SR to
initiate transmission of its uplink data. In another example, the UE may always select
SR to transmit delay-tolerant uplink data to the eNB. In another example, the UE can
select a first available opportunity, CB-UL or SR transmission opportunity whichever
occurs earlier, to initiate transmission of the uplink packet.
[0051] Embodiments can provide for multiple cyclic shifts and/or orthogonal cover code sequences
in a single grant. For example, an eNB can use Space Division Multiple Access (SDMA)
or Multiple User Multiple Input and Multiple Output (MU-MIMO) to improve uplink efficiency.
It can do so by scheduling UEs on the same time-frequency resources, but spatially
separated by configuring the users to transmit DMRS with different cyclic shifts.
The CB-UL can use the same technique to improve reception of CB-UL transmissions as
well. In this technique, the UE can be configured to select the cyclic shift from
an allowed set of cyclic shifts. For example, a UE can select from eight cyclic shifts
for a given DCI format 0 uplink transmission. The exact value of the cyclic shift
used by the UE can be indicated via the 3-bit field "Cyclic shift for DMRS and OCC
index" in the DCI format 0. An eNB can indicate multiple cyclic shift values via the
downlink grant.
[0052] For a first example, an eNB can send a single downlink message containing one MCS
(MCS0) and resource block assignment (RB0) and more than one cyclic shift value (CS0,
CS1, CS2). Upon receiving the message, a UE can select one of the cyclic shift values
based on a selection criterion (one of CS0, CS1, CS2) and can transmit on the resource
block assignment (RB0) using the indicated MCS value (MCS0). A second UE can select
one of the cyclic shift values based on a selection criterion (one of CS0,CS1,CS2)
and can transmit on the resource block assignment (RB0) using the indicated MCS value
(MCS0). Thus, the UEs can select different cyclic shift values and transmit on the
same resource blocks.
[0053] For a second example, an eNB can send a first downlink message, such as DCI, containing
one MCS (MCS0) and resource block assignment (RB0). The eNB can send a second message,
such as via RRC, indicating a set of cyclic shift values (CS0, CS1, CS2). Upon receiving
the first message, a UE can select one of the cyclic shift values based on a selection
criterion, such as one of CS0, CS1, CS2, where these values can be obtained from the
second message, and can transmit on the resource block assignment (RB0) using the
indicated MCS value (MCS0). A second UE can select one of the cyclic shift values
based on a selection criterion, such as one of CS0, CS1, CS2, where these values can
be obtained from the second message, and can transmit on the resource block assignment
(RB0) using the indicated MCS value (MCS0). Thus, the UEs can select different cyclic
shift values and transmit on the same resource blocks.
[0054] In another example, an eNB can configure multiple sets of cyclic shifts and/or orthogonal
cover code sequences via higher layers and indicate the particular set of cyclic shifts
and/or orthogonal cover code sequences that can be used in a given subframe via the
DCI message. An example of the indication is given in Table 6. For example, if a UE
receives a DCI indicating cyclic shift indication field of '10', then the UE can select
one value from {CS0, CS1, CS2} based on a selection criterion to transmit its DMRS.
At least one set can contain a plurality of cyclic shifts.
Table 6: Cyclic Shift Indication Field
Value of the Cyclic Shift Indication Field |
Description |
'00' |
First set of cyclic shifts configured by higher layers (e.g. {CS0}) |
'01' |
Second set of cyclic shifts configured by higher layers (e.g. {CS1, CS2}) |
'10' |
Third set of cyclic shifts configured by higher layers (e.g. {CS0, CS1, CS2}) |
'11' |
Fourth set of cyclic shifts configured by higher layers (e.g. {CS0, CS1, CS2, CS3,
CS4, CS5, CS6}) |
[0055] Embodiments can provide for selection of the uplink resource from multiple grants
based on a UE's coverage and eNB signaling. For example, an eNB can send multiple
contention-based uplink grants targeted towards UEs of different coverage levels in
a cell. For instance, an eNB can send a compact CB-UL grant, such as based on DCI
1C, using a smaller payload size to assist UEs in bad coverage and the eNB can send
a non-compact CB-UL grant, such as based on DCI 0/1A, using a slightly larger payload
size for other UEs that are in improved coverage. In this case, the grants can be
used appropriately by a UE based on its coverage level. For example, the UE can use
its downlink pathloss measurements and optionally a relative threshold indicated by
the eNB to appropriately select the correct uplink grant to transmit on. Thus, if
a UE detects multiple CB-UL grants with different payload sizes, it can select the
UL grant to use based on a set of pre-determined rules, including, for example coverage
level, downlink measurements, and other parameters. If a UE detects multiple CB-UL
grants with the same payload size, it can select one of the grants randomly, or each
grant may have an associated probability metric, such as embedded in the DCI, that
the UE can use to determine which grant to use. An example grant is shown below. An
example grant can include a 0/1A differentiation field, a frequency hopping flag,
a RB assignment field, a MCS field, a TPC for PUSCH field, a cyclic shift for DMRS
and OCC index selection field, a probability field, and an RA type field. The probability
field, such as a 2-bit field, can indicate one of four values, such as 0.25, 0.5,
0.75, and 1, that indicate the probability with which a UE can transmit on the uplink
resource indicated by the grant.
[0056] As another example, the set of CB-UL resources, such as signaled via higher layer
signaling, for UEs with different coverage can be different. For instance, the UEs
can be closer to the cell center, such as based on having an RSRP, measured in certain
subframes, such as indicated by higher layers, or almost blank subframes, or in subframes
containing Discovery Reference Signals, etc., above a signaled/specified threshold.
The closer UEs can get a larger CB-UL resource set, whereas UEs that are farther away
from the cell center may get a smaller, including the case of an empty set of CB-UL
resources, set for contention.
[0057] Embodiments can provide for UE detection at the eNB from the received uplink. For
example, if a UEID or C-RNTI is embedded in the MAC message, then the eNB can detect
it once the uplink TB is successfully decoded. Alternately, the UE may be able to
transmit its C-RNTI as uplink control information along with the data on the PUSCH.
In this case, the eNB can indicate separate parameters, such as delta parameters to
determine the number of REs for transmitting Uplink Control Information (UCI), for
the case when UCI is associated with a CB-UL. The C-RNTI may be encoded with an 8-bit
or a 16-bit CRC as well as some additional information, such as BSR and/or information
from the associated contention-based uplink grant.
[0058] Scrambling can be based on the cyclic shift and/or OCC index and/or other parameters
that a UE selects from the control message or using the CB-RNTI. For instance, the
scrambling sequence for uplink PUSCH transmission can be generated using:
where c
init can be the initialization seed used for scrambling sequence generator for PUSCH transmission,
n
RNTI can denote the RNTI, n
s can denote the slot number,
can be the cell Identifier, which may also be a virtual cell ID, q is a MIMO codeword
index (e.g. q = 1 for single codeword transmission), and f(cs) can denote a function
of the cyclic_shift (cs) and/or orthogonal cover code sequence associated with the
uplink transmission. As a first example, the function
f(
cs) =
cs. As a second example, the function
f(
cs) = 2
x ·
cs, where x can be an integer >0, signaled or fixed in the specification.
[0059] Embodiments can provide for PHICH/HARQ retransmissions for Contention-based uplink.
For example, if an eNB detects a cyclic shift based on DMRS but fails to detect the
uplink data, such as when CRC fails, then the eNB can signal the detected cyclic shift
on the downlink to request a retransmission from that UE. For example, the eNB can
transmit a dedicated resource addressed to the UE that used the particular cyclic
shift on the particular UL resource, such as when the eNB knows, based on a hashing
function, that a particular UE may have transmitted using the particular resource
with the particular cyclic shift. However, if the eNB fails to detect any transmission
on a contention-based resource on the uplink, then it can assume that the corresponding
resource was not used. If the eNB detects that there was a transmission on the contention-based
resource, but if it fails to detect uplink data, such as when CRC fails, or even a
DMRS cyclic shift or the UE that used the particular cyclic shift reliably, then the
eNB can use PHICH resource corresponding to uplink contention-based resource to indicate,
such as via NACK, that the uplink transmission failed, so the UE can then resort to
other means to handle packet failure. For example, the UE may re-attempt to transmit
the packet on another contention-based resource or the UE may receive a dedicated
resource from the eNB after a longer delay that it can use to transmit the packet.
[0060] LTE uplink HARQ is synchronous and can supports both adaptive and non-adaptive (re)transmission(s).
For FDD, there can be eight HARQ processes defined in the uplink for single-codeword
transmission mode and 16 HARQ processes for two-codeword transmission mode. In either
transmission mode, for contention-based uplink, a UE can likely use single codeword
transmission. For contention-based transmissions, separate HARQ process(es) can be
designated in addition to a regular HARQ processes. In another alternative, a same
HARQ process can be shared between contention-based to non-contention based transmission.
A NACK on PHICH resource corresponding to an uplink contention-based resource can
indicate to the UE that the corresponding uplink transmission has failed and that
the UE may have to retry transmitting the packet again. One or more consecutive NACKs
on PHICH to the UE can trigger an SR from the UE.
[0061] Embodiments can provide for power control. For example, power adjustment in response
to UE transmission on a particular resource on which CB uplink takes place can be
signaled by the eNB. TPC-CB-RNTI can signal adjustments for multiple resource allocations,
such as starting RB location, in the CB resource pool. For example, for a UE transmission
in subframe n on a CB-UL resource, the power adjustment can be sent in subframe n+4,
which can be used for a subsequent CB-UL transmission by the UE. The adjustment steps
may be different than the steps used for non-contention-based UL resources.
[0062] According to a possible example for power control, a UE can receive higher layer
signaling, such as via MAC or RRC indicating a set of resources for possible contention
based (CB) PUSCH transmission. The UE can also receive higher layer signalling indicating
open loop power control parameters that the UE can to use for CB transmission. The
parameters can include P0 and alpha, such as separate values of P0 and alpha for CB
transmission. If the UE has data in its buffer, in each DL subframe n in which PDCCH/EPDCCH
is monitored, the UE can check for DCI format 0/4 intended for the UE, such as with
DCI CRC scrambled with UE's C-RNTI.
[0063] If UE does not detect DCI intended for the UE, the UE can use a selection method
to select a subset of UL resources from the set of resources for possible CB transmission
in UL subframe n+k. The selection method can include UE the choosing one or more of
the following: a TB size, a number of RBs, a MCS index, DMRS cyclic shift, and DMRS
orthogonal cover code sequence. To determine the transmit power for CB-PUSCH transmission,
the UE can use the higher layer parameters, such as P0 and alpha, configured for CB
transmission, and any TPC adjustment received in a TPC command that corresponds to
the subset of UL resources that the UE has selected for CB-PUSCH transmission. The
TPC command can be received by the UE via a PDCCH message with DCI format 3/3A DCI
CRC is scrambled with an identifier associated with CB-PUSCH transmission, such as
a CB-TPC-PUSCH-RNTI. The PDCCH message with DCI format 3/3A can be received by the
UE in subframe n, such as for CB-PUSCH transmission in subframe n+k, the UE can use
the DCI format 3/3A received in subframe n for adjusting its PUSCH transmission power.
Alternately, once the UE is configured by higher layers with a set of resources for
possible CB PUSCH transmission, it can start monitoring DCI format 3/3A with CRC scrambled
by CB-TPC-PUSCH-RNTI. The DCI can contain TPC commands for multiple subsets of resources
within the set of resources for possible CB transmission. The UE can maintain a separate
TPC state for each subset and update it based on the TPC commands in each received
DCI format 3/3A with CRC scrambled by CB-TPC-PUSCH-RNTI. When the UE selects a particular
subset for PUSCH transmission, it can use the TPC state for that subset along with
open loop parameters to set its PUSCH transmission power for its transmission in that
subset of resources.
[0064] If UE detects DCI intended for the UE, the UE can use the RA allocation field in
the DCI to determine UL resources for PUSCH transmission in UL subframe n+k. The transmit
power used by the UE for PUSCH transmission can be based on open loop power control
parameters configured by higher layers for regular PUSCH transmission, and TPC adjustments
received in the DCI, such as a DCI that also has the RA allocation filed, and any
TPC adjustments received in DCI 3/3A with CRC scrambled by TPC-PUSCH-RNTI. The variable
k can be a number fixed in the specifications. For example, for LTE FDD frame structure,
k=4. For LTE TDD frame structure, k can depend on the specific UL/DL configuration
for the UE and can be, for example, 4 or 6.
[0065] In the event of a collision between a sidelink resource and a CB-UL resource, the
sidelink UE can drop the sidelink operation. For example, the UE can drop transmission
or reception of a sidelink signal in a CB-UL resource.
[0066] FIG. 5 is an example flowchart 500 illustrating operation of the wireless communication
device 110, such as a UE, according to a possible embodiment. The flowchart 500 can
be used to signal multiple resource assignments via a single grant. At 510, the flowchart
500 can begin. At 520, configuration information regarding a Downlink Control Information
(DCI) message for a Physical Uplink Shared Channel (PUSCH) transmission can be acquired.
[0067] At 530, the DCI message can be received on a Physical Downlink Control Channel (PDCCH)
in a first subframe. The DCI message can indicate a plurality of resource assignments
in a second subframe for an uplink carrier from which the UE can select one resource
assignment for transmission on the uplink carrier. The DCI message can be Cyclic Redundancy
Check (CRC) scrambled by a Radio Network Temporary Identifier (RNTI) that is indicated
via higher layers that are higher than a physical layer. Furthermore, the UE can have
a Cell Radio Network Temporary Identifier (C-RNTI) and a contention-based Cell Radio
Network Temporary Identifier (CB C-RNTI) configured via higher layers and the DCI
can be scrambled by the CB C-RNTI. Each resource assignment of the plurality of resource
assignments can have the same number of resource blocks. The number of resource assignments
can be explicitly or implicitly indicated in the DCI message. Additionally, the resource
assignments can be in an uplink grant. For example, a DCI message can include a plurality
of uplink grants, where each can include at least one resource assignment. A resource
assignment can contain resource blocks, other info such as transmit power and reference
signal configuration, and/or other information useful for transmitting on an UL. Sometimes
an uplink grant can have other information beyond the resource assignments.
[0068] At 540, a resource assignment can be selected from the plurality of resource assignments
using a selection criterion. The selection criterion can be a random selection of
the resource assignment from the plurality of resource assignments. The selection
criterion can also be based on at least one parameter measured by the UE. For example,
the selection criterion can be based on a measured parameter, such as Downlink Reference
Signal Received Power (DL RSRP), signal propagation path loss, uplink buffer status,
and/or any other useful parameter. Additionally, the UE can have a UE identifier and
the selection criterion can be based on at least a hashing function based on the UE
identifier.
[0069] At 550, a parameter can be determined for transmission of a data packet. According
to a possible embodiment, the UE can have a Cell Radio Network Temporary Identifier
(C-RNTI) and a cyclic shift and/or Orthogonal Cover Code (OCC) sequence can be determined
for a Demodulation Reference Signal (DMRS) for the transmission of the data packet
based on the C-RNTI. In some embodiments the Orthogonal Cover Code (OCC) sequence
may be fixed or pre-determined. According to another possible embodiment, a cyclic
shift and/or Orthogonal Cover Code (OCC) sequence can be determined for a DMRS for
the transmission based on at least one field indicated in the DCI message. According
to another possible embodiment, a cyclic shift can be determined for a DMRS for the
transmission and a scrambling initialization for PUSCH transmission can be selected
based on at least the determined cyclic shift for the DMRS for the transmission. According
to another possible embodiment, an Orthogonal Cover Code (OCC) sequence can be determined
for a DMRS for the transmission and a scrambling initialization for PUSCH transmission
can be selected based on at least the determined Orthogonal Cover Code (OCC) sequence
for the DMRS for the transmission.
[0070] At 560, a data packet can be transmitted on the PUSCH in a resource of the selected
resource assignment in the second subframe on the uplink carrier. At 570, the flowchart
500 can end.
[0071] FIG. 6 is an example flowchart 600 illustrating operation of the wireless communication
device 110, such as a UE, according to a possible embodiment. The flowchart 600 can
be used to signal multiple cyclic shifts via a single grant. At 610, the flowchart
600 can begin. At 620, configuration information regarding a Downlink Control Information
(DCI) message for a Physical Uplink Shared Channel (PUSCH) transmission can be acquired.
[0072] At 630, the DCI message can be received in a first subframe. The DCI message can
indicate a resource assignment and a modulation and coding scheme and indicating a
plurality of cyclic shifts from which the UE may select one cyclic shift for transmission
in a second subframe for an uplink carrier. The number of cyclic shifts in the plurality
of cyclic shifts indicated in the DCI message can be two or any other useful number
of cyclic shifts. The DCI message can implicitly indicate the number of cyclic shifts
in the plurality of cyclic shifts from which the UE can select one cyclic shift for
transmission. The DCI message can be received on a Physical Downlink Control Channel
(PDCCH) in a first subframe. The DCI message can indicate the resource assignment
and the modulation and coding scheme and can indicate a plurality of cyclic shifts
from which the UE may select one cyclic shift for transmission. The DCI message can
be Cyclic Redundancy Check (CRC) scrambled by a Radio Network Temporary Identifier
(RNTI) that is indicated via higher layers that are higher than a physical layer.
Additionally, the indication of a plurality of cyclic shifts can include an indication
of a plurality of cyclic shift and Orthogonal Cover Code (OCC) sequence pairs. A first
cyclic shift can be indicated using a cyclic shift for Demodulation Reference Signal
(DMRS) and OCC index field of the DCI message. A second cyclic shift can indicated
using a field used for Transmit Power Control (TPC) for a Physical Uplink Shared Channel
(PUSCH) and a field used for New Data Indicator (NDI). This can allow for three bits
for indicating a second cyclic shift. The cyclic shifts can also be indicated using
any other useful fields or information.
[0073] At 640, a cyclic shift can be selected from the plurality of indicated cyclic shifts
based on a selection criterion. The cyclic shift and an OCC sequence pair can be selected
from the plurality of indicated cyclic shift and OCC sequence pairs based on the selection
criterion. At 650, a scrambling initialization can be selected for the PUSCH transmission
based on at least the selected cyclic shift for DMRS.
[0074] At 660, a data packet can be transmitted on a Physical Uplink Shared Channel (PUSCH)
in a resource indicated by the resource assignment and modulation and coding scheme
and using a Demodulation Reference Signal (DMRS) based on the selected cyclic shift
in the second subframe on the uplink carrier. The data packet can be transmitted on
the PUSCH using a DMRS based on the selected cyclic shift and OCC sequence pair. At
670, the flowchart 600 can end.
[0075] FIG. 7 is an example flowchart 700 illustrating the operation of the wireless communication
device 110, such as a UE, according to a possible embodiment. The flowchart 700 can
be used for transmission by selecting from a set of higher layer configured resources,
such as for signaling multiple resource assignments, and the UE can select a resource
assignment based on a selection criterion. At 710, the flowchart 700 can begin.
[0076] At 720, an indication that indicates a set of frequency domain resource blocks for
possible Physical Uplink Shared Channel (PUSCH) transmission in an uplink subframe
can be acquired. For example, the resource set size can be the number of resource
blocks for possible PUSCH transmission. The subset of resource blocks can be a first
subset of resource blocks. The set of frequency domain resource blocks can be smaller
than an uplink transmission bandwidth configuration. For example, the uplink transmission
bandwidth configuration can be the uplink system bandwidth. The indication can be
a higher layer message from a layer higher than a physical layer. For example, the
higher layer message can be a RRC message, a MAC message, or any other higher layer
message or the indication can be in a physical layer message. For example, the indication
can include at least a physical layer message. The indication can be implicitly indicated
via a RACH configuration or can be otherwise indicated. The indication can also be
a bitmap indication that indicates whether or not each resource block in the set of
frequency domain resource blocks is assigned for possible PUSCH transmission.
[0077] At 730, a physical layer message can be received. The physical layer message can
indicate a second subset of resource blocks within the set of frequency domain resource
blocks for possible PUSCH transmission in the uplink subframe. At 740, higher layer
signalling can be received that indicates open loop power control parameters.
[0078] At 750, a subset of resource blocks can be selected from the set of frequency domain
resource blocks for possible PUSCH transmission based on a selection criterion. The
selection criterion can use at least a resource set size acquired from the indication,
a modulo function, and an identifier associated with the UE. The selected subset of
resource blocks can be one resource block. The selection criterion can use one or
more of a subframe number and a resource block aggregation level. For example, a resource
block aggregation level can be a number of resource blocks on which the UE transmits.
The UE can have a UE Cell Radio Network Temporary Identifier (C-RNTI) and the subset
of resource blocks can be selected in response to not detecting a DCI Format 0/4 with
a Cyclic Redundancy Code (CRC) scrambled by the UE C-RNTI on a Downlink (DL) control
channel for the uplink subframe. Selecting can also include selecting a cyclic shift
for a Demodulation Reference Signal (DMRS) for the PUSCH transmission in the uplink
subframe based on at least an identifier of the UE.
[0079] At 760, transmission power for PUSCH transmission in the subset of resources can
be determined based on the open loop power control parameters. At 770, at least one
other parameter can be determined for the PUSCH transmission. According to a possible
embodiment, a cyclic shift can be determined for a DMRS for the PUSCH transmission
and a scrambling initialization for the PUSCH transmission can be selected based on
at least the determined cyclic shift for the DMRS for the PUSCH transmission in the
uplink subframe. According to a possible embodiment, an Orthogonal Cover Code (OCC)
sequence for a Demodulation Reference Signal (DMRS) can be selected for the PUSCH
transmission in the uplink subframe based on at least an identifier of the UE. According
to a possible embodiment, an OCC sequence can be determined for a DMRS for the PUSCH
transmission and a scrambling initialization for the PUSCH transmission can be selected
based on at least the determined OCC sequence for the DMRS for the PUSCH transmission
in the uplink subframe.
[0080] At 780, a PUSCH can be transmitted in the selected subset of resource blocks in the
uplink subframe. The PUSCH may be transmitted in the selected first subset of resource
blocks in the uplink subframe only if the first subset of resource blocks belongs
to the second subset of resource blocks. The PUSCH may also be transmitted in the
selected subset of resource blocks regardless of whether the first subset of resource
blocks belongs to the second subset of resource blocks. At 790, the flowchart 700
can end.
[0081] It should be understood that, notwithstanding the particular steps as shown in the
figures, a variety of additional or different steps can be performed depending upon
the embodiment, and one or more of the particular steps can be rearranged, repeated
or eliminated entirely depending upon the embodiment. Also, some of the steps performed
can be repeated on an ongoing or continuous basis simultaneously while other steps
are performed. Furthermore, different steps can be performed by different elements
or in a single element of the disclosed embodiments.
[0082] FIG. 8 is an example block diagram of an apparatus 800, such as the wireless communication
device 110, according to a possible embodiment. The apparatus 800 can include a housing
810, a controller 820 within the housing 810, audio input and output circuitry 830
coupled to the controller 820, a display 840 coupled to the controller 820, a transceiver
850 coupled to the controller 820, an antenna 855 coupled to the transceiver 850,
a user interface 860 coupled to the controller 820, a memory 870 coupled to the controller
820, and a network interface 880 coupled to the controller 820. The apparatus 800
can perform the methods described in all the embodiments.
[0083] The display 840 can be a viewfinder, a liquid crystal display (LCD), a light emitting
diode (LED) display, a plasma display, a projection display, a touch screen, or any
other device that displays information. The transceiver 850 can include a transmitter
and/or a receiver. The audio input and output circuitry 830 can include a microphone,
a speaker, a transducer, or any other audio input and output circuitry. The user interface
860 can include a keypad, a keyboard, buttons, a touch pad, a joystick, a touch screen
display, another additional display, or any other device useful for providing an interface
between a user and an electronic device. The network interface 880 can be a universal
serial bus port, an Ethernet port, an infrared transmitter/receiver, a USB port, an
IEEE 1398 port, a WLAN transceiver, or any other interface that can connect an apparatus
to a network, device, or computer and that can transmit and receive data communication
signals. The memory 870 can include a random access memory, a read only memory, an
optical memory, a flash memory, a removable memory, a hard drive, a cache, or any
other memory that can be coupled to a wireless communication device.
[0084] The apparatus 800 or the controller 820 may implement any operating system, such
as Microsoft Windows®, UNIX®, or LINUX®, Android™, or any other operating system.
Apparatus operation software may be written in any programming language, such as C,
C++, Java or Visual Basic, for example. Apparatus software may also run on an application
framework, such as, for example, a Java® framework, a .NET® framework, or any other
application framework. The software and/or the operating system may be stored in the
memory 870 or elsewhere on the apparatus 800. The apparatus 800 or the controller
820 may also use hardware to implement disclosed operations. For example, the controller
820 may be any programmable processor. Disclosed embodiments may also be implemented
on a general-purpose or a special purpose computer, a programmed microprocessor or
microprocessor, peripheral integrated circuit elements, an application-specific integrated
circuit or other integrated circuits, hardware/electronic logic circuits, such as
a discrete element circuit, a programmable logic device, such as a programmable logic
array, field programmable gate-array, or the like. In general, the controller 820
may be any controller or processor device or devices capable of operating a wireless
communication device and implementing the disclosed embodiments.
[0085] According to a possible embodiment, the controller 820 can acquire configuration
information regarding a Downlink Control Information (DCI) message for a Physical
Uplink Shared Channel (PUSCH) transmission. The transceiver 850 can receive the DCI
message on a Physical Downlink Control Channel (PDCCH) in a first subframe. The DCI
message can indicate a plurality of resource assignments in a second subframe for
an uplink carrier from which the UE selects one resource assignment for transmission
on the uplink carrier. The DCI message can be Cyclic Redundancy Check (CRC) scrambled
by a Radio Network Temporary Identifier (RNTI) that can be indicated via higher layers
that are higher than a physical layer. Each resource assignment of the plurality of
resource assignments can have the same number of resource blocks. The controller 820
can select a resource assignment from the plurality of resource assignments using
a selection criterion. The apparatus 800 can have a UE identifier and the selection
criterion can be based on at least a hashing function based on the UE identifier or
can be based on any other useful selection criterion. The apparatus 800 can have a
Cell Radio Network Temporary Identifier (C-RNTI) and the controller 820 can determine
a parameter for a Demodulation Reference Signal (DMRS) for transmission of a data
packet based on the C-RNTI. The apparatus 800 can also have a Cell Radio Network Temporary
Identifier (C-RNTI) and a contention-based Cell Radio Network Temporary Identifier
(CB C-RNTI) configured via higher layers and the DCI can be scrambled by the CB C-RNTI.
The controller 820 can also determine a parameter for a DMRS for the transmission
based on at least one field indicated in the DCI message. For example, the parameter
can include a cyclic shift, an Orthogonal Cover Code (OCC) sequence, or other parameters
for a DMRS for a transmission. The transceiver 850 can transmit a data packet on the
PUSCH in a resource of the selected resource assignment in the second subframe on
the uplink carrier.
[0086] According to another possible embodiment, the controller 820 can acquire configuration
information regarding a Downlink Control Information (DCI) message for a Physical
Uplink Shared Channel (PUSCH) transmission. The transceiver 850 can receive a DCI
message in a first subframe. The DCI message can indicate a resource assignment and
a modulation and coding scheme. The DCI message can indicate a plurality of cyclic
shifts from which the UE may select one cyclic shift for transmission in a second
subframe for an uplink carrier. The number of cyclic shifts in the plurality of cyclic
shifts indicated in the DCI message can be two or any other useful number. For example,
a first cyclic shift can be indicated using a cyclic shift for Demodulation Reference
Signal (DMRS) and Orthogonal Cover Code (OCC) index field of the DCI message. A second
cyclic shift can be indicated using a field that is used for Transmit Power Control
(TPC) for a Physical Uplink Shared Channel (PUSCH) and a field used for New Data Indicator
(NDI). The DCI message can implicitly or explicitly indicate the number of cyclic
shifts in the plurality of cyclic shifts from which the UE can select one cyclic shift
for transmission. The controller 820 can select a cyclic shift from the plurality
of indicated cyclic shifts based on a selection criterion. The controller 820 can
also select a scrambling initialization for the PUSCH transmission based on at least
the selected cyclic shift for DMRS. The transceiver 850 can transmit a data packet
on a PUSCH in a resource indicated by the resource assignment and modulation and coding
scheme and using a DMRS based on the selected cyclic shift in the second subframe
on the uplink carrier.
[0087] According to a possible implementation the transceiver 850 can receive the DCI message
on a Physical Downlink Control Channel (PDCCH) in a first subframe. The DCI message
can indicate the resource assignment and the modulation and coding scheme and indicating
a plurality of cyclic shifts from which the UE may select one cyclic shift for transmission.
The DCI message can be Cyclic Redundancy Check (CRC) scrambled by a Radio Network
Temporary Identifier (RNTI) that is indicated via higher layers that are higher than
a physical layer.
[0088] According to another possible implementation, the indication of a plurality of cyclic
shifts can include an indication of a plurality of cyclic shift and Orthogonal Cover
Code (OCC) sequence pairs. The controller 820 can select the cyclic shift cyclic shift
and an OCC sequence pair from the plurality of indicated cyclic shift and OCC sequence
pairs based on the selection criterion. The transceiver 850 can transmit the data
packet on the PUSCH using a DMRS based on the selected cyclic shift and OCC sequence
pair.
[0089] According to another possible embodiment, the controller 820 can acquire an indication
that indicates a set of frequency domain resource blocks for possible PUSCH transmission
in an uplink subframe. The indication can be a bitmap indication that indicates whether
or not each resource block in the set of frequency domain resource blocks is assigned
for possible PUSCH transmission. The indication can also be any other indication
[0090] The controller 820 can select a subset of resource blocks from the set of frequency
domain resource blocks for possible PUSCH transmission based on a selection criterion.
The selection criterion can use at least a resource set size acquired from the indication,
a modulo function, and an identifier associated with the apparatus 800. The selection
criterion can also use one or more of a subframe number and a resource block aggregation
level. The transceiver 850 can transmit a PUSCH in the selected subset of resource
blocks in the uplink subframe.
[0091] According to a possible implementation the subset of resource blocks can be a first
subset of resource blocks. The indication can be a higher layer message from a layer
higher than a physical layer. The transceiver 850 can receive a physical layer message.
The physical layer message can indicate a second subset of resource blocks within
the set of frequency domain resource blocks for possible PUSCH transmission in the
uplink subframe. The transceiver 850 can transmit PUSCH in the selected first subset
of resource blocks in the uplink subframe only if the first subset of resource blocks
belongs to the second subset of resource blocks.
[0092] According to another possible implementation, the transceiver 850 can receive higher
layer signalling indicating open loop power control parameters. The controller 820
can determine a transmission power for PUSCH transmission in the subset of resources
based on the open loop power control parameters. The controller 820 can also select
a parameter for a Demodulation Reference Signal (DMRS) for the PUSCH transmission
in the uplink subframe based on at least an identifier of the apparatus 800. The controller
820 can further determine a parameter for a DMRS for the PUSCH transmission and can
select a scrambling initialization for the PUSCH transmission based on at least the
determined parameter for the DMRS for the PUSCH transmission in the uplink subframe.
The determined parameter can be a cyclic shift, an OCC, or any other parameter useful
for a DMRS for a PUSCH transmission in an uplink subframe.
[0093] The method of this disclosure can be implemented on a programmed processor. However,
the controllers, flowcharts, and modules may also be implemented on a general purpose
or special purpose computer, a programmed microprocessor or microcontroller and peripheral
integrated circuit elements, an integrated circuit, a hardware electronic or logic
circuit such as a discrete element circuit, a programmable logic device, or the like.
In general, any device on which resides a finite state machine capable of implementing
the flowcharts shown in the figures may be used to implement the processor functions
of this disclosure.
[0094] While this disclosure has been described with specific embodiments thereof, it is
evident that many alternatives, modifications, and variations will be apparent to
those skilled in the art. For example, various components of the embodiments may be
interchanged, added, or substituted in the other embodiments. Also, all of the elements
of each figure are not necessary for operation of the disclosed embodiments. For example,
one of ordinary skill in the art of the disclosed embodiments would be enabled to
make and use the teachings of the disclosure by simply employing the elements of the
independent claims. Accordingly, embodiments of the disclosure as set forth herein
are intended to be illustrative, not limiting. Various changes may be made without
departing from the scope of the disclosure.
[0095] In this document, relational terms such as "first," "second," and the like may be
used solely to distinguish one entity or action from another entity or action without
necessarily requiring or implying any actual such relationship or order between such
entities or actions. The phrase "at least one of" followed by a list is defined to
mean one, some, or all, but not necessarily all of, the elements in the list. The
terms "comprises," "comprising," or any other variation thereof, are intended to cover
a non-exclusive inclusion, such that a process, method, article, or apparatus that
comprises a list of elements does not include only those elements but may include
other elements not expressly listed or inherent to such process, method, article,
or apparatus. An element proceeded by "a," "an," or the like does not, without more
constraints, preclude the existence of additional identical elements in the process,
method, article, or apparatus that comprises the element. Also, the term "another"
is defined as at least a second or more. The terms "including," "having," and the
like, as used herein, are defined as "comprising." Furthermore, the background section
is written as the inventor's own understanding of the context of some embodiments
at the time of filing and includes the inventor's own recognition of any problems
with existing technologies and/or problems experienced in the inventor's own work.